The present invention relates to a multi-piece solid golf ball composed of a core, an envelope layer, an intermediate layer and a cover that have been formed as successive layers. More specifically, the invention relates to a multi-piece solid golf ball for professionals and other skilled golfers which is endowed with an excellent flight performance and good controllability.
A variety of golf balls have hitherto been developed for professionals and other skilled golfers. Of these, multi-piece solid golf balls in which the hardness relationship between an intermediate layer encasing the core and the cover layer has been optimized are in wide use because they achieve both a superior distance in the high head speed range and controllability on shots taken with an iron and on approach shots. Another important concern is the proper selection of thicknesses and hardnesses for the respective layers of the golf ball in order to optimize not only flight performance, but also the feel of the ball when played as well as its spin rate after being struck with a club, particularly given the large influence of the spin rate on control of the ball. A further key concern in ball development, arising from the desire that golf balls also have durability under repeated impact and suppress burr formation on the surface of the ball (have improved scuff resistance) when repeatedly played with different types of clubs, is how best to protect the ball from external factors.
The three-piece solid golf balls having an outer layer cover formed primarily of a thermoplastic polyurethane that are disclosed in, for example, JP-A 2003-190330, JP-A 2004-049913, JP-A 2004-97802 and JP-A 2005-319287 were intended to meet such a need. However, because these golf balls fail to achieve a sufficiently lower spin rate when hit with a driver, professionals and other skilled golfers desire a ball which delivers an even longer distance.
Meanwhile, efforts to improve the flight and other performance characteristics of golf balls have led to the development of balls having a four-layer construction, i.e., a core enclosed by three intermediate or cover layers, that allows the ball construction to be varied among the several layers at the interior. Such golf balls have been disclosed in, for example, JP-A 9-248351, JP-A 10-127818, JP-A 10-127819, JP-A 10-295852, JP-A 10-328325, JP-A 10-328326, JP-A 10-328327, JP-A 10-328328, JP-A 11-4916 and JP-A 2004-180822.
Yet, as golf balls for the skilled golfer, such balls provide a poor balance of distance and controllability or fall short in terms of achieving a lower spin rate on shots with a driver, thus limiting the degree to which the total distance can be increased.
Moreover, in the multi-piece solid golf ball disclosed in U.S. Pat. No. 6,994,638, the relationship between the thicknesses and hardnesses of the respective layers such as the intermediate layer and the cover is not disclosed. Hence, this ball is inadequate for achieving the spin rate-lowering effect on shots with a driver that is desired in a golf ball for the skilled golfer.